The Cytology of the External Ear Canal in the Normal Pig

External ear cytological results and resident flora of clinically normal alpacas (Vicugna pacos)

BACKGROUND

Otitis is common in alpacas. Suppurative otitis media/interna can be an extension from the external ear canal or from a respiratory infection. Cytological evaluation provides rapid and inexpensive information to assist in therapeutic decision; to date, there is no published information regarding the normal cytological results and flora of the alpaca external ear canal.

HYPOTHESIS/OBJECTIVES

To describe normal resident cytological findings and flora and possible variation over time, we sampled clinically normal alpaca external ear canals during two different seasons.

ANIMALS

Fifty privately owned, healthy alpacas of different ages and sexes in two northeastern United States flocks.

METHODS AND MATERIALS

One ear per alpaca had both cytological swabs (ectoparasites, inflammatory and epithelial cells, bacteria and yeast) and sterile swabs (bacterial and fungal cultures) taken. This was done in August 2017 and repeated in January 2018.

RESULTS

Yeast organisms were noted cytologically in 2-4% of the samples. Prevalence of total yeast genera was 6% in August and 30% in January. Cytologically, rod-shaped bacteria [maximum 4-10/high power field (HPF); median 0-0.5/HPF] were seen in 50% of alpacas in August and 26% in January. Coccal bacteria (maximum 6-10/HPF; median 0/HPF) were seen in 32% of alpacas in August and 16% in January. No statistically significant findings were noted between sampling months. Common bacterial genera isolated in August were Bacillus (44%), Arthrobacter (40%) and nonhaemolytic Staphylococcus (26%), and in January were Bacillus (42%) and Pantoea (38%).

CONCLUSIONS AND CLINICAL IMPORTANCE

This information may be useful when evaluating alpaca external ear canal samples, which subsequently may help dictate empirical therapy.